Paso del Cedral

How this one goes is settled by the water before anybody gets in. The drift here runs south to north, and at the slow end of its range Cedral is a low, broken, extremely fishy reef you can work at walking pace. At the fast end it is the ride Cozumel regulars talk about years later: coral going past underneath, the group strung out behind the guide.

The entry is onto flat ground, finger coral growing on sand, and this is the part a good guide slows down for. Splendid toadfish sit in crevices at the foot of the coral. Spotted drums work the shade nearby, and an octopus may be folded into a hole. Small caves in the sand here hold big lobster and sometimes a large green moray. The current is often at its least forgiving on this stretch, at the start, before there is any structure to get behind.

Then the reef arrives and the fish arrive with it. Grunts and snappers stack up in numbers the southern walls do not hold, and the shape of the reef is the reason: it is broken into pieces with gaps between them, and every gap is a pocket of still water. The gaps work the same way for a diver. Put a coral mound between yourself and the flow and you can move back and forth across and under the reef instead of being flown over it, which is why the middle third of this dive is where a photographer spends all of it.

The end is sand again, an open mound where barracuda hang and turtles feed, and where an eagle ray sometimes crosses in winter. By the time you reach it you are ready to go up.

The decision that changes the dive most is not on the reef at all. Along its outer edge the ground falls away, and the wall is deeper, faster and expensive in bottom time, with the bigger animals out in the blue off it. Reef or wall is one or the other. There is not enough gas in a single tank to do both properly, and the choice belongs on the boat rather than at depth.

The case for Cedral is fish, and it is made at a depth where the no stop clock never becomes the thing that ends the dive. Cozumel is sold on its walls, and this reef is not one. It is low and broken, twelve to eighteen metres for most of its length, and the encounters people remember here happen in that shallow band rather than out over the drop.

Nurse sharks come first. Operators up and down the island name them on this reef, and the reason is the ground itself: sandy gaps and overhangs between coral mounds are where a nurse shark spends the day. One diver, ducking behind a mound to get out of a ripping current, turned round to find a two metre nurse shark asleep a hand's width from his mask.

Second is the splendid toadfish, a fish found effectively nowhere but this island and listed by the IUCN as Endangered. It lives across the park. What is particular here is where: in the crevices of the flat opening section, on a relaxed profile with gas in hand, rather than somewhere you have to spend depth to reach.

Third is sheer quantity. Grunts and snappers in stacked schools, angelfish crossing the sand in pairs, morays that do not always stay in their holes: the reef reads busy in a way the big topography sites do not.

The park has treated this reef and the wall beside it as one place from the beginning. The 1998 management programme, which is the one still operating, names Paso del Cedral among the low intensity zone reefs alongside La Francesa, Dalila and the four Palancar sections1, and the park authority's own table of dive sites gives it one line and one classification, intermediate and deep2. Shops split it into two products and divers talk about two dives. All of them are describing one continuous piece of reef.

The honest other half is company. Plenty of boats work this strip, and divers who love the reef complain in the same breath about sharing it with a hundred of their closest friends. It is popular because it is good, and it is crowded for the same reason.

Timing decides more here than kit does. The usual slot for this reef is the second tank of the morning, and taking it on the first instead buys fewer groups on the strip and better light, at the cost of diving the day backwards from everybody else. At least one photographer who works this reef does exactly that and says why. The other window is late afternoon, when the light comes across the reef rather than straight down onto it.

Where to spend the frames is easier to answer. The broken middle third is the only stretch of a Cozumel drift you can genuinely hold position on. Get a mound between yourself and the current and twenty or thirty minutes over the same ground is realistic, and that is where the schools, the morays and the sleeping sharks are.

One picture here comes with a rule attached to it. Ask on the boat whether the guide knows which crevices hold a toadfish, because the ones who work this reef do; what must not follow is the animal being drawn out with a lure or a mirror. Disturbing a creature in its refuge is prohibited here, and a toadfish in its den is what that rule was written for.

Settle reef or wall before you are in the water. The published depths for the wall run to ninety feet and divers who have dived it record a hundred and twenty five, so a diver who has read the shallower figure and follows the guide over the edge can be at twice it within a minute. The reef line stays inside an Open Water card. The wall is an Advanced dive whatever a chart says about it, and on a strong day it is a fast one.

Separation is the thing to plan against. Eight divers behind one guide, several boats on the same strip, and water moving faster than anybody can swim adds up to a dive where losing the group is the likeliest problem you will have. Carry a surface marker, agree where you are going before you go in, and use the breaks in the reef when you want to stop, because stopping in the open just means being somewhere else by the time you look up.

Buy the nitrox. The reason on this profile is bottom time rather than depth: a long second dive on air here can start pressing the no decompression limit while there is still plenty of gas in the cylinder, and the richer mix takes that limit off the table. None of the gas caution that belongs to the island's deep southern dives applies at this depth.

Ask which reefs are resting before you commit to a day. Complexes are closed in turn so the coral can recover from disease, nothing is announced ahead of time on any page you can look up, and your shop is the only place a current answer exists. That question is sharper at this reef than at most, because the turns it has recently sat out fall in February and March, the two months the island sells hardest for its clear water.